nat works with ppp but not eth0

Anyone know why the router function of my computer works when I am dialed
up using an external modem but when i switch to using a cable modem for the
internet access, the router function doesn't seem to work because the other
computers on the lan cannot access the internet. They can't even ping the
dns server numbers successfully.

I could give my setup but I don't know if that would help. Here is a look:

localhost:~/1scripts# ifconfig
eth0 Link encap:Ethernet HWaddr 00:48:54:395:6E
inet addr:xxx.xxx.xxx.xxx Bcast:255.255.255.255
Mask:255.255.248.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:31980 errors:332 dropped:0 overruns:0 frame:0
TX packets:10176 errors:0 dropped:0 overruns:0 carrier:0
collisions:811 txqueuelen:100
RX bytes:5828111 (5.5 MiB) TX bytes:4067774 (3.8 MiB)
Interrupt:11 Base address:0x8000

eth0:0 Link encap:Ethernet HWaddr 00:48:54:395:6E
inet addr:192.168.0.3 Bcast:192.168.0.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:11 Base address:0x8000

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:476 errors:0 dropped:0 overruns:0 frame:0
TX packets:476 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:438256 (427.9 KiB) TX bytes:438256 (427.9 KiB)

roger <(E-Mail Removed)> wrote:

> Anyone know why the router function of my computer works when I am dialed
> up using an external modem but when i switch to using a cable modem for
> the internet access, the router function doesn't seem to work because the
> other computers on the lan cannot access the internet. They can't even
> ping the dns server numbers successfully.
>
> I could give my setup but I don't know if that would help.

This would clearly help. Please provide also the output of
"route -n" and "iptables-save".

Ciao, Horst
--
»When pings go wrong (It hurts me too)« E.Clapton/E.James/P.Tscharn

Horst Knobloch wrote:

> roger <(E-Mail Removed)> wrote:
>
>> Anyone know why the router function of my computer works when I am dialed
>> up using an external modem but when i switch to using a cable modem for
>> the internet access, the router function doesn't seem to work because the
>> other computers on the lan cannot access the internet. They can't even
>> ping the dns server numbers successfully.
>>
>> I could give my setup but I don't know if that would help.
>
> This would clearly help. Please provide also the output of
> "route -n" and "iptables-save".
>
> Ciao, Horst

don't think it has to do with any of those things. clearly the routing
works with dialup just fine. its a more complex issue!

On Fri, 30 Jan 2004 05:16:41 GMT, roger <(E-Mail Removed)> wrote:
> Anyone know why the router function of my computer works when I am dialed
> up using an external modem but when i switch to using a cable modem for the
> internet access, the router function doesn't seem to work because the other
> computers on the lan cannot access the internet. They can't even ping the
> dns server numbers successfully.
>
> I could give my setup but I don't know if that would help. Here is a look:
>
> localhost:~/1scripts# ifconfig
> eth0 Link encap:Ethernet HWaddr 00:48:54:395:6E
> inet addr:xxx.xxx.xxx.xxx Bcast:255.255.255.255
> Mask:255.255.248.0
> UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
> RX packets:31980 errors:332 dropped:0 overruns:0 frame:0
> TX packets:10176 errors:0 dropped:0 overruns:0 carrier:0
> collisions:811 txqueuelen:100
> RX bytes:5828111 (5.5 MiB) TX bytes:4067774 (3.8 MiB)
> Interrupt:11 Base address:0x8000
>
> eth0:0 Link encap:Ethernet HWaddr 00:48:54:395:6E
> inet addr:192.168.0.3 Bcast:192.168.0.255 Mask:255.255.255.0
> UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
> Interrupt:11 Base address:0x8000

It is probably NOT a good idea to use a single nic for both public and
private internet traffic since your local cable leg may see your private
traffic. But it should be possible, assuming that your LAN box(es) use
192.168.0.3 as their default gateway, and this box has proper routing and
iptables rules to masquerade your LAN.

I actually did that once to masquerade an alias 10.x.x.x subnet as a
192.168.x.x IP on the same nic and wire, but it was all behind a NAT
router, just so the 10.x.x.x could use the router expecting 192.168.x.x
IPs on its LAN side. It was easy to configure with SuSEfirewall2, but I
am not that knowledgeable about manually setting iptables rules.

--
David Efflandt - All spam ignored http://www.de-srv.com/

"roger" <(E-Mail Removed)> quoted and wrote in message
news:(E-Mail Removed) s.com

>>> Anyone know why the router function of my computer works when I am
>>> dialed up using an external modem but when i switch to using a
>>> cable modem for the internet access, the router function doesn't
>>> seem to work because the other computers on the lan cannot access
>>> the internet. They can't even ping the dns server numbers
>>> successfully.
>>>
>>> I could give my setup but I don't know if that would help.
>>
>> This would clearly help. Please provide also the output of
>> "route -n" and "iptables-save".
>
> don't think it has to do with any of those things. clearly the routing
> works with dialup just fine. its a more complex issue!

Maybe as complex as "echo 1 > /proc/sys/net/ipv4/ip_forward"? But of course
if your routing and iptables rulesets aren't configured to specifically
address the interface connected to the cable modem relative to the LAN
interface(s), then such problems as you're experiencing will most certainly
exist.

When you ask for help, and someone offers to examine your setup so as to
provide advice if it's in error, it's really rather counter-productive to
argue with them when you yourself are "in the dark".

Most people don't care to play guessing games with you.


tony

--
use hotmail for any email replies



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